This invention relates in general to semiconductor packaging and in particular to a system for achieving the desired bondlength of adhesives for bonding the housing of a semiconductor chip package to a heatsink.
For many semiconductor chip packages, particularly ceramic type packages, it is desirable to provide a heatsink for each package to facilitate the dissipation of heat generated by the chip. This is normally done by attaching a heatsink to the package using an adhesive such as an epoxy. In order for the epoxy to achieve the desired bonding strength to securely connect the heatsink to the package, it is usually desirable for the thickness of the epoxy layer between the heatsink and the package surface to be of a certain value depending on the type of epoxy used. Such thickness of the epoxy layer is also known as the bondlength of the epoxy. Therefore, when the heatsink is bonded to a surface of the semiconductor package, it is desirable to maintain a certain uniform clearance between the heatsink and the package, so that when the space between the package and the heatsink is filled by an epoxy layer, the bondlength of the epoxy layer is of a desired value. Such requirements for epoxy bonding are known to those skilled in the art.
A number of heatsink spacers have been proposed to set the spacing between the heatsink and the package so that the bondlength of the epoxy is of a desired value. Some of the conventional spacers used are discussed below in reference to figures. None of these prior art systems is entirely satisfactory. It is therefore desirable to provide an improved system for setting a spacing between the chip package housing and the heatsink so that the epoxy used has a predetermined bondlength.